Flat stitch forming and cover thread laying mechanisms for sewing machines

ABSTRACT

A compact, lightweight, high-speed machine of low-silhouette frame construction for forming flat seams such as those of stitch type 605 used, for example, for attaching elastic waistbands, borders, cuffs and collarettes to knit undergarments, athletic shirts and the like. The machine utilizes two or more needles each carrying a needle thread, to form, in cooperation with a looper, parallel rows of chain or double-lock stitches. A spreader which reciprocates in a straight line path and which cooperates with a special cover thread guide, places a cover thread in proper relation with all of the needle threads on the upper surface of the work piece. The looper is carried by an oscillating and horizontally reciprocating shaft and cooperates beneath the work piece with all of the needles to supply the looper thread for the chain stitches aforesaid. A single take-up is provided for all of the needle threads and the cover thread while a separate take-up is provided for the looper thread.

Siestak Dec. 4, 1973 FLAT STITCH FORMING AND COVER THREAD LAYINGMECHANISMS FOR SEWING MACHINES Primary Examiner--James R. BolerAttorney.lames D. Ock

[5 7] ABSTRACT 75 Inventor: Henryk Szostak, Oak Park, 111. compact,lightweight, high-Speed machine of silhouette frame construction forforming flat seams [73] AsslgneeZ Union speclal Machine Company such asthose of stitch type 605 used, for example, for

Chlcago, Ill. attaching elastic waistbands, borders, cuffs and col- [22]Filed: Apt 18, 1972 larettes to knit undergarments, athletic shirts andthe like. The machine utilizes two or more needles each PP N03 245,104carrying a needle thread, to form, in cooperation with a looper,parallel rows of chain or double-lock 52 U.S. c1. 112 162, 112/100Stitches A Spreader which reciprocates in a Straight 51 1m. (:1 00511/20 line P and'which cooperates with Special cover [58] Field 61 Search112/262, 162, 163, thread guide, places a cover thread in P p relation112/1 66 00 255 with all of the needle threads on the upper surface of vthe work piece. The looper is carried by an oscillating [56] ReferencesCited and horizontally reciprocating shaft and cooperates UNITED STATESPATENTS beneath the work piece with all of the needles to supply thelooper thread for the chain stitches aforesaid. Moffatt A Single p isprovided for of the needle 1,088,339 2/1914 Goodwin 112/100 X h d d h thd k 2,636,462 4 1953 Peterson 6118].. 112 162 t 6 cover Separate ta1,855,254 4 1932 Moffatt 112 100 Provlded the thread- 18 Claims, 16Drawing Figures ,1 I I W n a4 1%, Y/ K 3 -WE 44 66 H l I l [5b 1 I I1111 {LL46 2o 36 1 I l 1' l 22 i 32 33 l I I5 l l "I PATENTED BEE 4 I973SHEET 10F 6 PMENIED um 4 I915 SHEET 2 OF 6 PATENIEDBU: 4 I975 SHEET 3 BF6 FLAT STITCH FORMING AND COVER THREAD LAYING MECHANISMS FOR SEWINGMACHINES BRIEF DESCRIPTION OF THE INVENTION Considered first from'abroad standpoint the present invention provides as an end result asewing machine for forming flat seams by the use of a plurality ofneedles, a looper supplying a looper thread for interlocking withneedle-carried threads beneath a work piece and a spreader for formingloops in a cover thread to lay the cover thread beneath theneedle-carried threads-on the upper surface of the work piece. Themachine differs in a broad sense from those conventional flat-bedmachines which form similar multi-needle stitches in that it embodiesthe desirable characteristics of lowsilhouette frame structure andquiet, smootho peration and the cover thread and a separate take-up, forthe.

looper thread. The spreader having this particular movement and thecover thread guiding arrangement cooperating therewith for laying acover thread are believed to be novel whether they are combined with theparticular needle actuating, or looper or take-up mechanisms disclosedherein or are combined with othe mechanisms for the same generalpurposes.

BACKGROUND OF THE INVENTION U.S. Pat. No. 1,707,068 granted Mar. 26,l929-to Rubel discloses a flat bed sewing machine which has threeneedles, a looper, a spreader and a cover thread guide all arranged toform a flat seam of the type formed of the machine of the presentinvention/In this Rubel patent both the spreader and the cover threadguide are mounted on vertical axes for-oscillatory motion relative toone another in horizontal planes above the work piece.

U.S. Pat. No. 2,107,918 granted Feb. 8, 1938 to Thompson et al disclosesa multi-needle flat bed sewing, machine in which a spreader whichoscillates about a.

vertical axis cooperates with a fixed cover thread guide and a coverthread eyelet which moves'vertically with theneedles for laying a coverthread. This particular patent discloses the cover thread handling andlooper mechanisms as used in a currently manufactured flat bed machinebut for a more extensive disclosure of the operation of the spreader,cover thread guide and 'eyelet reference is made to an earlier U.S. Pat.No. l,405,855 granted Feb. 7, 1922 to Moffatt wherein similar mechanismis used. In theseThompson, and Moffatt disclosures the cover threadguide is fixed close to the plane of oscillation of the spreader and itis provided with a curved slot through which the cover. thread extendsafter it has passed downwardly through.

an eyelet which moves up and down with theneedles. The combined motionsof the spreader and the eyelet cause the cover thread to slide back andforth between.

stable positions at opposite ends of the curved slot, thus to positionthe cover thread ahead of one needle and behind the other. The presentinvention adapts a cover thread guide and vertically movable eyeletarrangement similar to that shown in these patents for cooperation witha spreader which reciprocates in a horizontal straight line path.

U.S. Pat. Nos. 2,636,462 granted Apr. 28, 1953 to Peterson et al.,2,704,042 granted Mar. 15, 1955 to Wallenberg et al., and 3,101,686granted Aug. 27, 1963 to Hayes, as well as U.S. application Ser. No.35,450 filed May .7, 1970, now U.S. Pat. No. 3,688,71], by Szostak etal., are illustrative of the development of the over-edge sewingmachines having low-silhouette, compact frame structures and which runquietly and smoothly at very high operating speeds. As will be pointedout hereinbelow the machine of the present invention embodies thesegeneral features of such over-edge machines in a flat seam sewingmachine. The overedge machines disclosed in the patents and thecopending application just referred to employ a looper, an overedgelooper and an underedge looper to cooperate with a plurality of needlesto form the overedge stitches. The looper disclosed in the presentapplication is the same as that disclosed in said application Ser. No.35,450, while the overedge and underedge loopers, disclosed in saidcopending application and said patents, along with trimmers and otherequipment peculiar to overedge machines are omitted from the machine ofthe present invention. From the standpoint of background however, itshould be noted that the overedge loopers in said patents and saidcopending application are mounted on horizontal shafts having bothoscillating and reciprocating motions.

U.S. Pat. No. 659,482 granted Oct. 9, 1900 to Klemm discloses a singleneedle overedge sewing machine in which a looper is carried by a barwhich reciprocates without oscillatory motion in a horizontal planeabove the work piece.

' BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front view of a machineembodying the present invention, the view being partly in elevation andpartly in section;

FIG. 2 is a vertical sectional view taken along the line 2--2 in FIG. 1;

FIG. 3 is an elevational view taken from the left-hand side of FIG. 1;

FIG. 4Jis a fragmentary plan view with parts in section;

FIG. 5 is a fragmentary elevational view, taken from the right-hand sideof FIG. 1 and showing certain parts in section;

FIG. 6 is a fragmentary elevational view, taken as is F IG. 3, andshowing certain parts in section;

FIG. 7 is a fragmentary vertical sectional view showing the looperthread control means;

FIG. 8 is a detail elevational view, with parts in section, showing theneedle carrying and driving means;

FIG. 9. is an enlarged rear view of the presser foot;

FIG. 10 is an enlarged left-hand side view of the FIG. 13 is aperspective view of stitch type 605 as produced by a machine embodyingthe present invention;

FIG. 14 is a fragmentary top plan view illustrating the operation of thecover thread laying mechanism;

FIG. is a view similar to FIG. 14 but showing the parts in a differentposition; and

FIG. 16 is a perspective view of the needle and cover thread eyelets andthe common take-up member which operates on the needle and coverthreads.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT The embodiment of theinvention illustrated herein is a sewing machine for forming flat seamswhich has the characteristics of smooth and quiet operation at very highspeeds and a low-silhouette frame structure heretofore possessed bycertain overedge stitching machines. The mechanism and the framestructure are similar in many respects to that shown in co-pending U.S.application Ser. No. 35,450 filed May 7, 1970 by Szostak et al, which inturn is similar in many respects to U.S. Pat. No. 3,101,686 granted Aug.27, 1963 to Hayes. However, the present embodiment differs substantiallyfrom said application and patent in that it is a multiple-needle machinefor forming flat seams and in particular is adapted to form seamsembodying a stitch type 605 in work pieces wherein the greater depth ofthroat afforded by earlier types of flat bed machines may not berequired. Thus, for instances, the present embodiment will serveadmirably for attaching elastic waistbands to knitted undergarments,attaching borders to the neck and armholes of knitted athletic shirts,and attaching cuffs and collarettes to knitted undergarments.

As shown in the present drawings the embodiment of this invention iscontained within a low-silhouette frame structure which houses most ofthe operatingmechanism of the machine. Housing 10, as best shown inFIGS. 1, 2 and 4, has a main section 11 with a bottom plate 12 securedthereto for retaining a quantity of lubricant in the base portion of theframe to insure proper lubrication of most of the relatively movingparts of the machine which have some frictional engagement. A framesection 13, which is shown as a separate element of the frame structure,assists in providing an open space within the frame of the machine forreceiving various operating parts. The frame section 13a (FIG. 1),carries a spring-retaining housing 13b which, in a well known manner,carries a spring for urging a presser foot 130 downwardly to retain workpieces against a work supporting surface or throat plate 1 la thatextends horizontally within a plane about midway of the overall heightof the-machine. The top of the frame is provided with a closure section14 which is preferably removably attached to the portion 13 of the frameso as to normally enclose the main housing portion of the frame butwhich permits access when necessary, to the interior of the housing.

Suitably journalled within the frame 11 in a manner more fully disclosedin the above-mentioned Hayes patent is a main drive shaft 15 which asviewed in FIG. 1, extends outwardly beyond the righthand side of thehousing. The righthand or outward end of shaft 15 has secured thereto aconventional pulley 15a and a hand wheel 15b by which the main driveshaft 15 may be rotated. As is usual, a suitable belt connection isprovided from an electric motor and clutch unit to pulley 15a fornormally rotating the main drive shaft 15 at a comparatively high speedwhen the clutch is closed under mechanical or automatic control.

The machine embodying the present invention is provided with arelatively light-weight needle carrier member 16 (see FIG. 5) havingbearing members 16a and 16b which surround a guide member 17. As is thecase in said application Ser. No. 35,450, the guide 17 is held in afixed position extending vertically in order to provide a vertical pathfor reciprocation of needles carried by the needle carrier 16. Also, asshown in said application Ser. No. 35,450, adequate provision is madefor lubrication between the bearing members 16a and 16b and the verticalguide 17.

Reciprocation of the needle carrier 16 in a vertical direction isaccomplished by an arm 18 secured to a shaft 19. The outward end of arm18, as more fully described in said application Ser. No. 35,450, carriesa pin 180 (see FIG. 8) on which is journalled a roller element 18b whichcooperates with a U-shaped surface 16e of the needle carrier 16. As willbe apparent, rocking of thearm 18 about the shaft 19 will cause verticalmovement of needle carrier 16 as a result of the rolling contact betweenthe roller 18b and surface 16c of the needle carrier. Rocking movementis imparted to the shaft 19 on which arm 18 is secured by connectionstypical of a machine of this character. Thus (referring to FIG. 2) apitman 20 having an enlarged portion 20a at its lower end is connectedby suitable anti-friction bearings with a crank portion 15a of the maindrive shaft 15. At its upper end the pitman 20 carries a pin 200 bywhich the pitman is pivotally connected with an arm 21 secured to theshaft 19 whereby rotation of the main drive shaft 15 producesoscillation of the needlecarrier actuating shaft 19.

Referring now to FIG. 5, the lower portion of the needle carrier 16 isprovided with a needle retaining portion 160 adapted to receive theupper ends of a plurality of needles, indicated generally at N in saidFIG. 5, and which will be described in more detail hereinbelow.

Referring now to FIG. 1 it will be observed that there are three needlesN1, N2 and N3 mounted in the needle retaining portion 16c of the needlecarrier 16. It will be understood that three such needles will beprovided' when it is desired to form a flat seam which includes threeparallel rows of chain stitches. However, it will be further understoodthat only two needles may be used in those instances wherein it isdesired to produce two rows of parallel stitching.

Still referring to FIG. 1, it will be observed that the needlesN,separately identified as N1, N2 and N3, are supplied respectively withthreads TNl, TN2 and TN3 from a suitable source (not shown) and throughguiding and take-up means to be described hereinbelow.

As shown in FIG. 1 a looper 22 is positioned to work beneath the throatplate or work supporting portion 11a of the frame of the machine. Thelooper 22 is operated, by means similar to or identical with that shownin said application Ser. No. 35,450, for reciprocation horizontallytowards the right and left, as viewed in FIG. 1, and for limited rockingor avoiding movement about'the axis of a hollow looper bar 23. Briefrefer;

ence to FIG. 3 at this juncture will reveal the location 7 of the looper22 and bar 23 relative to the needles as viewed from the lefthand end ofthe machine. Referring back to FIG. 1, the looper bar 23 is arranged forlongi tudinal reciproctory movement and also for oscillatory movementthus to produce the looper motions deand cooperates with the lower endof va pitman- 28, the

upper end of which cooperateswith a spherical portion 29 of a crank 30formed on the main drive shaft 15.

Thus, rotation of shaft 15 is transmitted, through the 1 linkage justdescribed} to the looper bar 23 to reciprocate the same towards theright and left in a smooth and noiseless fashion. The looper bar 23extends through means including a cam guide sleeve 31 which is con-:centric with and secured to a looper barsleeve 32"immediatelysurrounding the looper bar 23. The inner'or looper bar sleeve 32 is heldagainst lengthwise move-: ment and is mounted in bearings 33 and 34 foroscillation about the axis of the bar 23. Referring to FIGS. 1 and 2 itwill be observed that the outer or cam guide sleeve 31 and the innerlooper bar sleeve 32are slotted, as indicated at 35, to receive a camblock 36 pinned to the looper bar 23. Thus the cam block 36 may slideback and fourth in the slots incident to reciprocation of the looper bar23 along its axisjrelatively tothe sleeves 31 and 32. The sleeves 31 and32 are secured by a set-screw 31a to a link 37 and a looper avoidconnecting rod 38 the upper end of which is carried by a crank section(not shown) on the main drive shaft 15.

The rocking motion thus imparted to cam guide sleeve, 31 about the axisof looper bar23 is imparted to bar 23 viewed in FIG. 1 imparted tolooper-.22 by lengthwise reciprocation of looper bar 23 is quiteextensive inasmuch as the looper 22 is designed for cooperation withthree needles in the forming of typical chain stitches by interlocking alooper thread TL with the needle threads TNl', TN2 and TN3. Theoscillatory motion imparted rected from a suitable source (not shown) toa bracket 40 and through an eyelet 42 from which it extends downwardlyto a looper thread take-up mechanism 44' and thence upwardly through aneyelet 46 on looper 22 to the active part of the looper. The loopertake-up mechanism 44 is the same as that shown in said application Ser.No. 35,450. Thus in FIG. 7 it will be observed that the looper take-upmechanism 44 includes a cam 48 fixed upon the main drive shaft 15, asupport plate 50 and a castoff plate 52 between whichthe looper threadTL is passed. Actuation of the looper't'ake up mechanism 44 is properlytimed with respect to' the movements of the looper 22 beneath the throatplate 1 1a, so as to tighten the looper thread around the needl'ethreads in customary manner. v

The lefthand end portion of the drive shaft- 15 as viewed in FIG. 1 alsocarries suitable eccentrics for reciprocating feed bars 54 and 56 (alsosee FIG. 3) which in turn carry conventional feed dogs 58 and 60 whichoperate through appropriate slots 62 in the throat plate Ila (alsoseeFIG. 12).

The various parts of the machine as so far described in detail areeither identical with or very similar'to corresponding parts in saidapplication Ser. No. 35,450. It will be appreciated that severalcomponents of the machinedisclosed in said application are omitted fromthe present machine, such omitted parts being those that are intended tocooperate to perform the overedge stitching operation disclosed in saidapplication. How ever the parts now to be described differ in structureand functionfrom anything disclosed in said application Ser. No. 35,450,and are specifically provided for the'purpose of cooperating with theparts already described in the formation of flat seams, for example,seams embodying a stitch type 605.

In the present machine, as viewed first in FIG. 1, a spreader 64 isfixed to the lefthand end of a spreader shaft 66 journalled in a bearing68 for axial horizontal reciprocation devoid of any oscillatory movementabout the axis of shaft 66. The shaft 66 is reciprocated by a Y-shapedlink 70 which, in turn, is driven by a bell crank lever 72 pivoted on across shaft 74 and connected by a spherical end piece .76 with a pitman78 the lower end of which is driven by a crank portion (not shown) onthe main drive shaft 15. The Y-shaped link 70(see FIG. 4) is connectedat end one to a pin 80 secured to the spreader shaft 66 by a set screw82. At its other end the link 70 is connected to the fork 84.01 bellcrank 72 by a pin 86' (see FIG. 1). By connecting the link 70 as justdescribed between the bell crank.72 and spreader shaft 66 it is assuredthat the shaft 66 will be reciprocated longitudinally while being heldagainst any' rotational movement abouts its own axis. In this connectionalso see FIG. 4 wherein the disposition of the link 70 with respecttothe shaft 66 is shown in plan.

. just ahead of the needles and above the work supporting surface (notshown in'FIG. 3) of throat plate 11a. Referring back to FIG. 1 thelefthand end of the laterally'extending portion of spreader. 64 isbifurcated to form a thread receiving slot 88. The position of thespreader64 shown in FIG. 1 is'that assumed at the end oflefthandreciprocation of the spreader shaft 66 and in this position itwill be notedthat the thread engaging slot 88 is well to the left of thevertical paths of the needles N. The position thus shown' in FIG. 1corresponds with that shown in the detailed view in FIG. 14. The po=sition assumed by the spreader 64 at the righthand end of its excursionis-shown in the detailed FIG. 15. As will be apparent from FIG. 14 the Ilefthand end of the spreader 64 is not only bifurcated to form the slot88 but also the upper arm of the bifurcated end is cut off at an angleas indicated at 90 in said FIG. 14 so as to retain the cover thread TCduring the leftward stroke of the spreader 64.-

The cover thread TC, FIG. 1, extends from a suitable source, not shown,through an eyelet 92 in bracket 40, an eyelet 94 in bracket 96 anddownwardly through an eyelet 98 in a bracket 100 mounted on the needlecarrier 16. From eyelet 98 the cover thread TC extends downwardly to acover thread guide 102 and through a guide slot 104 formed in guide 102.The cover thread guide 102 is adjustably secured by screws 106 workingin slots 108, to a bracket 110 on the machine. The cover thread guide102 includes a downwardly extending leg 112 which positions thedownwardly inclined portion of guide 102 (see FIG. 3) in which slot 104is formed just above the plane in which the spreader 64 reciprocates.The operation of the spreader 64 and cover thread guide 102 incooperation with the cover thread TC will be described after thefollowing descrip-v tion of the take-up-mechanism which operates notonly upon the thread TC but also upon all of the needle threads N.

As mentioned above the source of supply of the several threads used inthis machine has not been shown.

Ordinarily such source may comprise an appropriate number of spools on aspool stand. Also, there has not been shown herein the thread tensioningmechanism for applying individually adjustable tension to each of thethreads. Such a mechanism is shown in said application Ser. No. 35,450and it or any other suitable mechanism may be employed with the presentmachine. Referring now to FIG. 4 the threads TL, TC and TN], TN2 and TN3coming from suitable tensioning mechanism enter the machine from theupper left hand portion .of FIG. 4. The looper thread TL goes directlyto eyelet 42 in bracket 40 and from there to the looper thread take-upmechanism as has been described above. The needle threads TNl, TN2 andTN3, and the cover thread TC, however, enter a common take-up deviceindicated generally at 114 in FIG. 4 and from there extend through abracket 116 having four eyelets (not shown) to the bracket 40.

The course of cover thread TC from bracket 40 to the cover thread guide102 has been described above.

The needle threads TN 1, TN2 and TN3 pass through suitable eyelets, notnumbered, in bracket 40 and from there extend through suitable eyelets,not numbered, in bracket 96. From bracket 96 the needle threads extend,see FIG. 1, through a three-eyelet bracket 118 on the upper part ofneedle carrier 16 and through three eyelets, not numbered, in bracket100 on the lower part of needle carrier 16, to the eyes, respectively ofthe three needles N1, N2 and N3.

The common take-up mechanism 114 referred to i above in connection withFIG. 4 includes a take-up member 120 secured to a clamp collar 122adjustably mounted on the needle actuator rock shaft 19 for oscillatingmotion therewith. Referring now to FIGS. 6 and 16 the takeup member 120cooperates with a bracket 124 having laterally spaced portions 126 and128 (see FIG. 16) which straddle the take-up member 120 and whichrespectively, are provided with upstanding portions 130 and 132 eachhaving four eyelets (not numbered) for the threads. The bracket 124 isadjustably secured to the upper surface of the machine frame by a screwand slot connection 134, 136 (see FIG. 6) and also is provided with thebracket 116 having four eyelets (not numbered) for the threads to guidethem to bracket 40 described above.

In all of the figures of the drawing except FIGS. 15 and 16 the partsare. shown in the positions assumed when needles N are in theiruppermost position withdrawn from a work piece and ready to startdonwardly toward the work piece. In FIG. 15 the parts. are shown in thepositions assumed when the needles N are in their lowermost position,extending downwardly through the work piece and ready tostart upwardmotion. In FIG. 16 it may be assumed that the needles have startedmoving downwardly.

Referring now to FIG. 16 the needle threads TNl, TN2 and TN3 and thecover thread TC enter the takeup mechanism 114 where they are threadedindividually through the eyelets in upstanding portion 132 of bracket124. From those eyelets all of the threads extend into contact with theforward surface of take-up member and then individually through theeyelets in upstanding portion and bracket 116. As will be apparent fromFIG. 16, with reference particularly to FIGS. 3 and 6 forward orclockwise rocking of the takeup member 120 will exert a pull on all ofthe needle threads and the cover thread within the span between theupstanding portions 130 and 132 of bracket 124. Such rocking occursduring the downward stroke of the needles and the pull exerted on thethreads by member 120 is effective to withdraw lengths of the threadsfrom the supply and tensioning means and also is effective, actingagainst the tensioning means, to draw backwardly on the needle and coverthreads. The pull-off and take-up actions required for forming thestitches are thus performed, the unique feature here being that a commontake-up and pull-off mechanism is provided to act upon all of the needlethreads as well as on the cover thread.

Since the illustrated embodiment of the present invention employs threeneedles N1, N2 and N3 the presser foot and the throat plate shown hereinare adapted for operation with three needles, although, as noted above,there may be instances wherein the user may require only two needles.The presser foot indicated generally at 130 in FIG. 1 is shown in FIGS.9, 10 and I1 and it includes a presser foot bottom 140 which is adaptedto be yieldingly pressed downwardly on a work piece, when required, bythe arm 142 (FIG. 3) which, in turn, is pressed by the spring containedwithin spring housing 13b (FIG. 3). The presser foot bottom 140 isprovided with an opening 144 of suitable size to accommodate the threeneedles N 1, N2 and N3. The throat plate 11a, FIG. 12, in addition tothe slots 62 through which the feed dogs 58 and 60 work; is providedwith an opening, generally indicated at 146, which is shaped toaccommodate the three needles N1, N2 and N3.

7 As will have been observed in connection with FIG. 1 the needles aresoset in the needle holder 16 that the points thereof lie at differentlevels, the pointof needle N1 being at a lowermost level, the point ofneedle N2 being at an intermediate level and the point of needle N3being at an uppermost level, all with respect to the plane in which awork piece is supported on throat plate 110. Still referring to FIG. 1it will be noted that the cover thread TC, as it extends from slot 104of cover thread guide 102 tr the thread-receiving slot 88 at thebifurcated end of spreader 64, extends in front of the two left-handneedles N1 and N2 and at a level above the points of these two needles,while it extends at a level beneath the point of the right-hand needle 9N3. Bearing in mind that the needles N1, N2 and N3 are in the uppermostposition in the path of vertical reciprocation as shown in FIG. 1,attention is now directed to FIG. 14 wherein the parts are in that sameposition. In this FIG. 14 several previously formed stitches are shown,the fabric in which they are formed being omitted, and in the positionof parts illustrated the feed dogs 58 and 60 are in the middle of theirfeeding stroke whereby it may be assumed that the previously formedstitches are ready to continue moving towards the rear, that is,upwardly as viewed in FIG. 14, and that the needles N1, N2 and N3 areready to start to move downwardly. The portion of the cover thread TCjust discussed in connection with FIG. 1, extends in front of needles N1and N2 and extends behind the axis along which needle N3 will descend asthis portion of the stitching cycle proceeds. Therefore, as the needlesmove downwardly and feed dogs 58 and 60 end their stroke, the needles N1and N2 will penetrate the work piece behind said portion of the coverthread TC and the needle N3 will penetrate in front of said portion. Atthe time of penetration the previously formed stitches will have movedrearwardly into the position shown in FIG. 15 and upon completion of thedownward stroke of the needles the take-up mechanism, described above,will have functioned to pull backwardly on cover thread TC, and thespreader 64 will have moved to the right releasing the cover thread TC,the position ofall of the parts at this moment being as shown in FIG.15. Also, in this position the bracket 100 and eyelet 98 will have moveddownwardly with the needles so as to lie very close to the upper surfaceof the cover thread guide 102.

In the portion of the stitch-forming cycle just de scribed theparticular shape of the slot 104 in cover thread guide 102 and therelation between said slot and the eyelet 98 in bracket 100, which moveswith the needles, and the straightline path of movement of spreader 64,have played an important part in achieving desired disposition of thecover thread TC beneath the needle threads on the upper surface ofa workpiece. Thisbest may be understood by describing the succeeding halfcycleas if it were leading up to the position of parts shown in FIG. 14.Thus, starting with FIG. 15, the needles will begin to move upwardly,the take-up mechanism 114, due to counterclockwise rocking of member 120(FIG. 16), will start to let off the needle and cover threads and thespreader 64 will start to move toward the left as viewed in FIG. 15. Theadvancing spreader 64 will engage the cover thread TC beneath the coverthread guide 102 and as let-off continues will form a loop in the coverthread by pulling thread downwardly through eyelet 98 and the slot 104,eventually to position the cover thread TC as it is shown in FIG. 14. Inthe meantime eyelet 98, in bracket 100, is moving upwardly with theneedles, thus progressively lengthening the use of the illustratedembodiment of the invention.

the span of thread TC extending downwardly from eyelet 98 to slot 104 incover thread guide 102. Still referring to FIG. 15 it will be observedthat the slot 104 is elongated and has a dog-leg with a high point 148about midway of the length of the slot. Instead of a dog-leg shape asshown the slot 104 could be curved to provide a high point equivalent tothe high point 148. The purpose of the particular shape of slot 104 isto assure that the cover thread TC will move into a stable position-atthread at any given moment. Thus, when the needles N1, N2 and N3 aredown, as in FIG. 15, and the eyelet 98 is very close to the cover threadguide 102, the length of cover thread TC extending upwardly from thelast stitch formed by needle N3 through the slot 104 and to the eyelet98 will tend to lie at a forwardly inclined angle widely divergent fromthe vertical. Instead however, the changingrelationship of parts willslide the thread TC forwardly along slot 104 so as to reach a stableposition at the lower end thereof as viewed in FIG. 15. This forwardpulling of the cover thread TC will have been effected by the increasinghorizontal component of force exerted thereon as the needles and eyelet98 were moving downwardly toward the position shown in FIG. 15.Accordingly, as the needles and eyelet 98 start to rise and the spreader64 moves forwardly to engage the cover thread TC beneath cover threadguide 102 the horizontal component of force diminishes and the verticalcomponent increases with the result that the thread TC will be pulled tothe opposite end of slot 104 to assume the position shown in FIG.

To assist in understanding ofthe movement of the cover thread TC, justdescribed, reference is made to FIG. 3 wherein the solid line positionsof parts are those assumed when the needles N are up. The path of coverthread TC from eyelet 98 to cover thread guide 102 is relatively longand not much inclined from the vertical. However, in the broken lineposition of certain parts in FIG; 3 the bracket 100 and eyelet 98 areshown in positions 100A and 98A and the path of thread TC is shown in aposition TCA which would be assumed when the needles are down in theposition indicated at NA. From a comparison of these two paths for thecover thread TC the reason for movement of the thread from one end tothe other of slot 104 will be clear/Also, it will be apparent that whenthe cover thread is in position TCA, in FIG. 3, it lies directly in thepathof travel of spreader 64 so that the slot 88 thereof will engage thecover thread to carry the same into the loop illustrated in FIG. 14during upward movement of the needles.

Referring back to FIG. 14 it now will be understood that because'thecover thread TC has moved to the rearward,-or upper, end of slot 104during the rise of the needles the straight-line movement of spreader 64has formed a loop in the cover thread TC wherein the length of threadextending from slot 104 to the thread engaging surface 90 of thespreader lies at an angle starting from behind needle N3 and extendingin front of needles N1 and N2. This is the position at which the abovedescription of operation started and the machine I is now ready forrepetition of the complete cycle.

In FIG. 13, several stitches are illustrated in a perspective view.These are stitches of the type formed by It will be understood thatinstead of using three needles to form the illustrated stitch, one mayuse two needles or more than three needles, if desired, which would oneend or the other of slot 104 depending upon the resultant direction ofthe combined forces acting on the form stitches somewhat similar tothose illustrated in FIG.13.

vVarious modifications and variations in details of the illustratedembodiment of the present invention may be resorted to by those skilledin the art without departing fromthe scope of the claims.

What is claimed is:

1. In a sewing machine, stitch forming devices for forming a flat seamcomprising a plurality of needles reciprocable in a substantiallyvertical plane and each carrying a needle thread, a throat plate havinga work supporting surface lying in a substantially horizontal plane andhaving an opening for passage of said plurality of needles through saidthroat plate, a looper carrying a looper thread and disposed beneathsaid throat plate for cooperation with said needles to form a pluralityof parallel rows of stitches, and a spreader operating solely in astraight line reciprocatory motion wholly above said throat plate forlaying a cover thread in position for engagement beneath all of saidneedle threads as said parallel rows of stitches are formed.

2. A sewing machine in accordance with claim 1 in which said straightline motion of said spreader is in a substantially horizontal path.

3. A sewing machine in accordance with claim 2 in which said spreader iscarried by a shaft having a substantially horizontal straight linemotion.

4. A sewing machine in accordance with claim 2 in which said spreader iscarried by a shaft having a substantially horizontal axis and in whichsaid shaft has only an axial reciprocatory motion.

5. A sewing machine in accordance with claim 2 in which said looper hasa motion in a path which is substantially parallel with the path of saidspreader.

6. In a sewing machine, stitch forming devices for forming a flat seamcomprising a plurality of needles reciprocable in a vertical plane andeach carrying a needle thread, a throat plate having a work supportingsurface lying in a horizontal plane and having an opening for passage ofsaid plurality of needles through said throat plate, a looper carrying alooper thread and disposed beneath said throat plate for cooperationwith said needles to form a plurality of parallel rows of stitches, aspreader operating solely in a straight line reciprocating motion whollyabove said throat plate for forming a loop in a cover thread forpenetration by certain of said plurality of needles, and cover threadguide means cooperating with said spreader to direct one strand of eachloop in said cover thread between two adjacent needles.

7. A sewing machine in accordance with claim 6 in which said straightline motion of said spreader is in a substantially horizontal path.

8. A sewing machine in accordance with claim 7 in which said spreader iscarried by a shaft having a substantially horizontal straight linemotion.

9. A sewing machine in accordance with claim 7 in which said spreader iscarried by a shaft having a substantially horizontal axis and in whichsaid shaft has only an axial reciprocatory motion.

10. A sewing machine in accordance with claim 7 in which said looper hasa motion in a path which is substantially parallel with the path of saidspreader.

11. A sewing machine in accordance with claim 7 in which said coverthread guide means includes a guide plate fixed to said machine in aposition closely overlying said spreader, and an eyelet mounted abovesaid guide plate for movement with said needles vertically toward andfrom' said guide plate, and said guide plate having a curved elongatedslot formed therein for passage of said cover thread from said eyeletand through said slot into the path of said spreader, the combinedmotions of said spreader and said eyelet relative to said guide platecausing said cover thread to slide between stable positions at oppositeends of said slot thus to direct said one strand of each loop in saidcover thread between said adjacent needles.

12. A sewing machine in accordance with claim 11 in which said straightline motion of said spreader is in a substantially horizontal path.

13. A sewing machine in accordance with claim l2 in which said spreaderis carried by a shaft havinga substantially horizontal straight linemovement.

14. A sewing machine in accordance with claim 12 in which said spreaderis carried by a shaft having a substantially horizontal axis and inwhich said shaft has only an axial reciprocatory motion.

15. A sewing machine in accordance with claim 12 in which said looperhas a motion in a path which is substantially parallel with the path ofsaid spreader.

16. A sewing machine in accordance with claim 1 in which there isprovided a common take-up means for all of said needle threads and saidcover thread.

17. A sewing machine in accordance with claim 6 in which there isprovided a common take-up means for all of said needle threads and saidcover thread.

18. A sewing machine in accordance with claim 11 in which there isprovided a common take-up means for 'all of said needle threads and saidcover thread.

' 1 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,77 57 Dated December M, 1973 Inventor(s) Henryk SCak It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

On the title page "Attorney James D. Ock" Q should be "James D.v Bock--Col. 8, line 4 "donwar'dly" should be -downwardly Col. 8, l ne 63 "tr"should be -t ov I Claim 6, line 11 "reciprocating" should be--reciprocatory-- Name of Assignee should be changed fromd Union SpecialMachine Company" to --Union Special Corporation-- Signed and sealed this23rd day of April 1971;.-

(SEAL) Attest:

EDWARD I' 'I.1*LETOHER,JR. C. MARSHALL DANN Attesting OfficerCommissionerof." Patents

1. In a sewing machine, stitch forming devices for forming a flat seamcomprising a plurality of needles reciprocable in a substantiallyvertical plane and each carrying a needle thread, a throat plate havinga work supporting surface lying in a substantially horizontal plane andhaving an opening for passage of said plurality of needles through saidthroat plate, a looper carrying a looper thread and disposed beneathsaid throat plate for cooperation with said needles to form a pluralityof parallel rows of stitches, and a spreader operating solely in astraight line reciprocatory motion wholly above said throat plate forlaying a cover thread in position for engagement beneath all of saidneedle threads as said parallel rows of stitches are formed.
 2. A sewingmachine in accordance with claim 1 in which said straight line motion ofsaid spreader is in a substantially horizontal path.
 3. A sewing machinein accordance with claim 2 in which said spreader is carried by a shafthaving a substantially horizontal straight line motion.
 4. A sewingmachine in accordance with claim 2 in which said spreader is carried bya shaft having a substantially horizontal axis and in which said shafthas only an axial reciprocatory motion.
 5. A sewing machine inaccordance with claim 2 in which said looper has a motion in a pathwhich is substantially parallel with the path of said spreader.
 6. In asewing machine, stitch forming devices for forming a flat seamcomprising a plurality of needles reciprocable in a vertical plane andeach carrying a needle thread, a throat plate having a work supportingsurface lying in a horizontal plane and having an opening for passage ofsaid plurality of needles through said throat plate, a looper carrying alooper thread and disposed beneath said throat plate for cooperationwith said needles to form a plurality of parallel rows of stitches, aspreader operating solely in a straight line reciprocating motion whollyabove said throat plate for forming a loop in a cover thread forpenetration by certain of said plurality of needles, and cover threadguide means cooperating with said spreader to direct one strand of eachloop in said cover thread between two adjacent needles.
 7. A sewingmachine in accordance with claim 6 in which said straight line motion ofsaid spreader is in a substantially horizontal path.
 8. A sewing machinein accordance with claim 7 in which said spreader is carried by a shafthaving a substantially horizontal straight line motion.
 9. A sewingmachine in accordance with claim 7 in which said spreader is carried bya shaft having a substantially horizontal axis and in which said shafthas only an axial reciprocatory motion.
 10. A sewing machine inaccordance with claim 7 in which said looper has a motion in a pathwhich is substantially parallel with the path of said spreader.
 11. Asewing machine in accordance with claim 7 in which said cover threadguide means includes a guide plate fixed to said machine in a positionclosely overlying said spreader, and an eyelet mounted above said guideplate for movement with said needles vertically toward and from saidguide plate, and said guide plate having a curved elongated slot formedtherein for passage of said cover thread from said eyelet and throughsaid slot into the path of said spreader, the combined motions of saidspreader and said eyelet relative to said guide plate causing said coverthread to slide between stable positions at opposite ends of said slotthus to direct said one strand of each loop in said cover thread betweensaid adjacent needles.
 12. A sewing machine in accordance with claim 11in which said straight line motion of said spreader is in asubstantially horizontal path.
 13. A sewinG machine in accordance withclaim 12 in which said spreader is carried by a shaft having asubstantially horizontal straight line movement.
 14. A sewing machine inaccordance with claim 12 in which said spreader is carried by a shafthaving a substantially horizontal axis and in which said shaft has onlyan axial reciprocatory motion.
 15. A sewing machine in accordance withclaim 12 in which said looper has a motion in a path which issubstantially parallel with the path of said spreader.
 16. A sewingmachine in accordance with claim 1 in which there is provided a commontake-up means for all of said needle threads and said cover thread. 17.A sewing machine in accordance with claim 6 in which there is provided acommon take-up means for all of said needle threads and said coverthread.
 18. A sewing machine in accordance with claim 11 in which thereis provided a common take-up means for all of said needle threads andsaid cover thread.